CROSS-CONTAMINATION OF THE GNOMES IN HUMAN HAMSTER CELL HYBRIDS BY MULTIPLE SHORT RECOMBINATION EVENTS/

We have isolated sites of de novo rearrangements from interspecific ce ll hybrids. Of 147, 000 clones screened from a human/hamster hybrid ge nomic library, 14 clones were found with homology to both human and ha mster repetitive DNA sequences. Five of these clones contained recombi nation events involving less than 13 kb of DNA, three with human DNA r ecombined into a section of hamster DNA, and two with hamster DNA reco mbined into human DNA. None of the clones involving human L1 sequences were found to be de novo transposition events, but simply, short reco mbination or insertion events. Considering the apparent random nature of these events, they are likely to involve unique as well as repetiti ve sequences and also involve integration into the homologous as well as heterologous chromosome sets. These results suggest that the chromo some sets in somatic cell hybrids may be randomly contaminated with sm all DNA segments derived from either set of chromosomes.